The present invention relates to a method and apparatus for ejecting target mass. In particular, but not exclusively, the present invention provides a method and apparatus for a fast mass ejection device able to eject liquid and/or liquid vapour quickly and over relatively long distances from an ejection chamber in which a quantity of liquid is stored. Still more particularly, but again not exclusively, the present invention relates to a fuel injector and method for injecting fuel.
There is a need in a number of industries for mass ejection devices. That is to say, devices which will send out a spray of liquid and liquid vapour at a fixed or variable rate and over a desired distance. Preferably there is a need for a spray of liquid and liquid vapour to occur at a fast rate and over a great distance. In such systems the term “throw” is often referred to as a characteristic of a spray. The throw of material is defined as the distance traveled divided by the length of a chamber from which the spray is ejected.
Various examples of mass ejection devices are known such as fire extinguishers, ink jet printers, air bag igniters, fuel injectors for motor engines and gas turbines, pilot flames, etc. In each of these there are specific problems associated with the device in question, however, for each applied technology there is a continuing desire to be able to eject liquid and liquid vapour quickly and over a large distance.
By way of example of a problem specific to an application of mass ejection systems, reference is made to a gas turbine reigniter. In the igniter of a gas turbine, the conventional approach to reignite gas in a combustion chamber is to pass a current between two electrodes of a reigniter and create for a short while a mixture of electrically charged radicals. This is illustrated more clearly in FIG. 1 in which a conventional reigniter 10 is shown including an outer electrode 11 which is generally cylindrical in shape with an internally located pellet 12. A central electrode 13 is located within the pellet and by passing a current between the two electrodes 11, 13 a mixture of electrically charged radicals (that is when the gas molecules split temporarily into charged components referred to as a plasma). This plasma only lasts for a fraction of a second before recombining and losing its charge. The charge is then used to ignite combustion in a main combustion chamber of the main engine. A problem with such known reigniters is in getting the mixture to be ejected as ejected material via the exit orifice 14 far enough and to remain charged long enough to perform its objective function. The ejected material 15 has been used to ignite the kerosene or other usual gas turbine engine fuel.
By way of a further example of a problem specific to an application of mass ejection systems, reference is made to a fuel injector. Prior art fuel injectors use electro-mechanical nozzles and a pre-pressurised fuel to produce a finely atomised spray. Fuel is pressurised within a chamber and an electromagnetic coil lifts a needle of its seal so fuel can squeeze through the nozzle's aperture through an intake valve. Control of the timings of the release of this pressurised liquid is controlled by electronics. This has the disadvantage of costly and complex materials which are prone to error and require many working parts.
A further example of a use of a mass ejector system is in a pilot flame for furnace and boilers used in the energy industry or land based gas turbines.